PSEUDOTSUGA 271 



A large tree 30-61 m. high, with a trunk 1.20-3 m - i n diametej. 

 Wood light, hard, not strong, rather close grained. 



Relative specific gravity 0.5182 



Percentage of ash residue 0.42 



Approximate relative fuel value 51.61 



Coefficient of elasticity in kilograms on millimeters . . 1375. 



Ultimate transverse strength in kilograms 388. 



Ultimate resistance to longitudinal crushing in kilograms 8747. 



Resistance to indentation to 1.27 mm. in kilograms . . 1622. 

 (Sargent) 



Low, moist bottoms and rocky ridges ; very common and reaching its 

 greatest development in western Oregon and Washington, often form- 

 ing extensive forests (Sargent); valley of the Columbia at Donald, 

 at 1000 feet elevation, thence westward to Stony Creek at 3500 feet, 

 thence the predominant tree to the Selkirk summit (Macoun); Alaska, 

 thence south along the islands and coast of British Columbia and 

 through the Rocky Mountains to the Bitter Root Mountains of Idaho ; 

 the western slopes of the Rocky Mountains of Montana ; through the 

 Cascade Mountains of southern Oregon and the coast ranges to Marin 

 County, California, between 1000 and 4000 feet elevation (Sargent). 



14. * PSEUDOTSUGA, CARR. PLATES 46 AND 47 



Transverse. Growth rings and summer wood very variable. Resin pas- 

 sages prominent and well formed without thyloses, but with thick- 

 walled epithelium. Resin cells more or less numerous on the outer 

 face of the summer wood, not very resinous, and usually distinguished 

 by their (i) thinner walls and somewhat advanced position, and (2) 

 by the sieve-plate structure of the terminal walls. 



Radial. Ray tracheids present. Ray cells with thick and coarsely pitted 

 terminal walls. Wood tracheids always with flat and close spirals in 

 double series. 



Tangential. Fusiform rays present, generally narrow, the central tract 

 composed of i small resin canal without thyloses, but with small and 

 thick-walled epithelium cells ; the ray cells thick-walled throughout. 



SYNOPSIS OF SPECIES 



Ray cells (tangential) distinctly oval or oblong. 



Pits on the lateral walls of the ray cells small, round or oval, at first 



3-7, soon 1-3, per tracheid. 



1. * P. Douglasii. 



Ray cells (tangential) broad, distinctly squarish, more rarely oval or round. 

 Pits on the lateral walls of the ray cells conspicuously larger than in 

 i, the orifice lenticular, 3-6 per tracheid. 



2. P. macrocarpa. 



